Modern communication systems comprise a multitude of different devices and apparatuses which communicate with each other. The data rates used in the communication are steadily increasing. In addition, some devices and/or apparatuses may be divided into separate parts and must be connected using high data rate connections.
Some of these connections utilize standardized or widely accepted interfaces. One of such interfaces is called Common Public Radio Interface or CPRI. CPRI is a serial interface, typically implemented with optical medium and it supports a wide range of data rates.
Apparatuses or separate parts of apparatuses or devices may typically have independent clocks. The area or section served by a single clock may be denoted as a clock domain. When data crosses clock domain borders, timing uncertainty arises. Typically the amount of uncertainty is of the order of one clock cycle of the receiving clock domain. The timing uncertainty presents problems especially when complex line and forward error correcting is used. Complex FEC requires complex processing which may comprise several clock domain crossings and coded data does not comprise any explicit timing reference points.